Parsed egglog commands.

Egglog.Commands is a small native-backed handle returned by Egglog.parse/1 or Egglog.Program.parse/1. Use it when the same command sequence will be run repeatedly and you want egglog parsing to happen once.

The commands are still executed by native egglog; this module only keeps the parsed AST resource alive. The original source is retained as well, so query-local inspection helpers such as Egglog.Program.eval/4 and Egglog.Program.lookup/5 can inspect parsed command input without requiring callers to keep a second copy of the string.